A protein can be hollow.Logical formLearned from2 sentences. Grooves can be hollow.Logical formLearned from2 sentences. Box-formations can be hollow.Logical formLearned from2 sentences. Some agates can be hollow.Logical formLearned from2 sentences. A penetration can be hollow.Logical formLearned from2 sentences. (Organ injuries) can be hollow.Logical formLearned from2 sentences. An (organ injury) can be hollow.Logical formLearned from2 sentences. A flake can be hollow.Logical formLearned from2 sentences. A bling can be hollow.Logical formLearned from2 sentences. Laughs can be hollow.Logical formLearned from2 sentences. Perforations can be hollow.Logical formLearned from2 sentences. (Iron balls) can be hollow.Logical formLearned from2 sentences. A center of constructs can be hollow.Logical formLearned from2 sentences. Arteries can be hollow.Logical formLearned from2 sentences. A roosting-place can be in hollow trees.Logical formLearned from2 sentences.